At least 13,000 acres burned by Pawnee Fire in Northern California

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An air tanker drops retardant on a wildfire burning above the Spring Lakes community.

(CNN)The Pawnee Fire burning in Northern California's Lake County has now consumed 13,000 acres and is Cal Fire's number one priority, according to state authorities.

So far, there have been no reports of injuries or casualties. But 22 buildings have been destroyed, with 600 more threatened by flames. Mandatory evacuation orders are in place for some communities and about 1,500 people have been forced from their homes.

A vehicle scorched by a wildfire remains in a clearing on Wolf Creek Road near Clearlake Oaks.

"I just got in this truck and left ... and left everything there. It changes directions, it burns real quick," Lake County resident Alan Phillips told CNN affiliate KTXL. "They say leave, leave."

But state fire officials warn that residents should get out while they can. "When you are asked to evacuate, that's what we ask you to do. It's for your own safety," Cal Fire Capt. Amy Head told KTXL, adding that wind patterns have made fighting the Pawnee fire difficult.

Grim memories of Santa Rosa

More than 200 personnel have been monitoring the fire from agencies such as the Lake County Sheriff's Office, the US Forest Service and the California Conservation Corps.

Flames were first reported early Saturday evening driven by "low relative humidity, erratic winds and above normal temperatures," according to Cal Fire.

The cause of the fire is under investigation.

Lake County is about 100 miles northwest of the capital, Sacramento.

The Pawnee Fire is bringing up grim memories of last year's fires in Santa Rosa, which is about an hour and a half from Lake County. Wildfires there ravaged more than 245,000 acres, destroyed nearly 7,000 structures and killed 42 people, making it one of the worst fires in California history.